Abstract
Abstract Aims Leaf nutrient resorption is sensitive to changes in soil nutrients. However, the effects of N deposition on nutrient resorption efficiency (NuRE) in plant macro-nutrients remain unclear. Poplar (Populus deltoids) is one of the most extensively cultivated hardwood species worldwide. We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition. Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar (P. deltoids) plantations (8- and 12-year-old stands) in a coastal region of eastern China. We measured soil and foliar (green and senesced leaves) concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) for a series of N addition treatments including N0 (0 kg N ha−1 yr−1), N1 (50 kg N ha−1 yr−1), N2 (100 kg N ha−1 yr−1), N3 (150 kg N ha−1 yr−1) and N4 (300 kg N ha−1 yr−1). Important Findings Consistent for (both) 8- and 12-year-old stands, N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio). N resorption efficiency–P resorption efficiency (NRE–PRE) scaling slopes were consistently less than 1.0 under N addition. These results suggest that NRE generally decouples from PRE within each N treatment. Moreover, these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations. Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.
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Claims 6
Claim · model-written summary
Nitrogen addition generally did not affect nutrient resorption efficiency or stoichiometry in either stand age.
- Treatment
- N additione0
- Outcome
- NuRE and stoichiometrye0
- Direction
- did not affecte0
- Qualifier
- 8- and 12-year-old standse0
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Consistent for (both) 8- and 12-year-old stands, N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio).”
t0“poplar”
Claim · model-written summary
Calcium resorption efficiency was an exception to the generally null nitrogen addition response.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio).”
t0“poplar”
Claim · model-written summary
The calcium to magnesium resorption efficiency ratio was an exception to the generally null response.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio).”
t0“poplar”
Claim · model-written summary
Nitrogen versus phosphorus resorption efficiency scaling slopes were below one under nitrogen addition.
- Treatment
- N additione0
- Outcome
- N resorption efficiency–P resorption efficiency (NRE–PRE) scaling slopese0
- Direction
- less thane0
- Value
- 1.0e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N resorption efficiency–P resorption efficiency (NRE–PRE) scaling slopes were consistently less than 1.0 under N addition.”
t0“poplar”
Claim · model-written summary
Nutrient resorption efficiency was positively related to green leaf nutrient concentrations.
- Organ / stage
- green leafe0
- Outcome
- NuREe0
- Direction
- positivee0
- Qualifier
- green leaf nutrient concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“positive relationships between NuRE and green leaf nutrient concentrations.”
t0“poplar”
Claim · model-written summary
Growth in 12-year-old poplar plantations was nitrogen limited in coastal eastern China.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.”
t0“poplar”
The same questions in other papers
nitrogen · nutrient: content · Populus (poplar)Positive and negative results
1 paper in the same direction as this paper · 5 in the opposite direction
- positive
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- positive
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See all 7 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.